The photographic news

• Bandzählung: 29.1885
• Erscheinungsdatum: 1885
• Sprache: Englisch
• Signatur: F 135
• Vorlage: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: SLUB Dresden
• Rechtehinweis: Public Domain Mark 1.0
• URN: urn:nbn:de:bsz:14-db-id1780948042-188500006
• PURL: http://digital.slub-dresden.de/id1780948042-18850000
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• Sammlungen: Fotografie
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244 THE PHOTOGRAPHIC NEWS. [April 17, 1835. of the picture, that must be made to fit two points (A', B') in a fiducial line. If the precaution, of which I am about to speak, has not been taken, the process of making the fit will consist of a set of separate and tedious attempts, until the fit proves satisfactory. At the beginning of each attempt, the picture has to be removed a step further off, or nearer, as the case may be, and there must be a fresh focussing and a fresh adjustment for position. In my plan, I arrange the fiducial line A' B' so that one or other of its two ends—say A'—corresponds exactly with the optical axis of the camera. Then, however much the portrait may be moved to or fro parallel to the optical axis, and how ever large may be the corresponding focussing change in the length of the body of the camera, the point A in the image of the print will remain glued, as it were, to A' in the fiducial line. After the line A B has been once super imposed on A' B' there will remain only the position of B to be attended to. In my apparatus I simultaneously work the carriage with one hand, and the focussing arrange ments with the other, and the image, while retaining its sharpness, continuously waxes or wanes, as the case may be, in its size. The horizontal line that bisected the pupils at first, always continues to do so, and the vertical line still continues to stand exactly half-way between the pupils. I go on steadily screwing until the parting of the lips in the image coincides with the lower horizontal fiducial line, and then the adjustment is complete. In a solidly-made camera, it is easy to find, and mark once for all on its ground glass screen, the exact position of the intersection of the screen with the optical axis of the lens. If we adjust the camera so that the image shall be of about the same size as the original picture, a little subsequent enlargement or reduction of the image will not require any sensible change of distance between the object and the ground glass screen. The lens can be moved to and fro a short distance, with the effect of altering the size of the image without sensibly affecting its definition. I therefore tested the position of the optical axis of my camera under these conditions. The camera and the portrait were both fixed, and as I screwed the lens in or out, the image grew smaller or larger without varying materially in sharpness, and expanded and contracted from a central radiant point, whose exact position I very soon ascertained. This being fixed, the parallelism of the tramway of the carriage to the optical axis was rectified until the to and fro movement of the carriage had no effect in causing the image A to separate from the fiducial A'. When all was satisfactorily arranged, the process of reduction to scale became swift, and very interesting to perform. Beautiful as the adjustments of my camera are, I must honestly confess that if I had to begin quite afresh, I should employ a much more disconnected process. It would be an improvement on that which I first tried, which was merely to take prints that happened to be nearly of the same size, to adjust them under fiducial marks scratched on glass, and then to press down upon them a hinged flap, which carried two points that pricked two “ register ” marks in the margin of the print. The prints were successively suspended on two pins driven into the wall opposite the camera, the pins being passed through the register holes. What I should do now would be to deal chiefly with group portraits. I formerly disparaged them for the pur pose of composite portraiture as being too small and ill- defined, but they are now so frequently made on a large scale, and with good definition, and they form such useful collections of persons of the same family, profession, or race, that I should be inclined, when I have next to occupy myself with composites, to make much use of them, and to make the composites of the same size as they. Having selected portraits differing little in size, I should cut them out and paste them severally on cards, I should carefully measure the distance in each from eye line to lip line, under a lens in good light, and I should write the measurement on the card. I should also carefully estimate and write down the proper numberof units of exposure, having regard to the vigour of the portrait. Then I should adjust and attach the cards to similar frames, guided by fixed fiducial lines, regarding only the upper horizontal line in fig. 1, with its short cross marks, and its intersection, the vertical line, and disregarding the mouth line. Lastly, 1 should prop these frames in succession in front of the camera. The points to be attended to would be, first, that the frames should be accurately propped. This would best be done by two notches, like inverted V’s (N AN) cut in their lower edge, each notch straddling over a stout round peg firmly fixed at right angles to the wall. The adjustment to scale would be greatly facilitated by making the ccm- posites of the same average size as the prints, because in that case, as already remarked, a slight screwing to and fro of the lens will change the size of the image without sensibly affecting its definition. I should then carefully graduate by trial the head of the focussing screw in such a way that I need only turn it until the figure that came opposite to a fixed index was the same as that of the measurement written on the card, to ensure that the image should be correct to scale. As the point of intersection of the horizontal and vertical fiducial lines would lie io the optical axis of the camera, the image would always fall into its right place. I should use a common lens for the camera, one that did not define too sharply ; but I should be very particular about the goodness of its mounting and focussing screw. These hints will suffice; the details must be filled in by the reader. The fault I find with my present camera is loss of light, due to the reflection of the image upwards from an enclosed mirror, and to the necessity of viewing it through a piece of (thin plane) glass inclined at 45°, the upper surface of which reflects the illuminated fiducial lines scratched on a blackened plate that is mounted at its side with a light behind it. I also think that my camera is too much of a jack-of-all-trades, and that I should get on much better if the portraits were successively prepared at leisure, making the actual photo graphy of them a quick and simple process. In the plan I have just mentioned, all the preparations would be gone through in good light, and without any hurry. Then the photography would be swift, and it would become feasible to make many trials, leaving out one or other of the more doubtful portraits. As it is, I find the production of even a single composite to be an anxious and fatiguing work, and if any part of the complicated process goes wrong, all has to be repeated. There is no reason why this anxiety and fatigue should not be avoided. There is nothing respecting composites that I should more gladly hail than the invention of a simple optical method of combining many images into one, so as to judge of the effect of a photographic composite before making it. Nothing can be better for optically combining two por traits than the prism of doubly refracting spar that I have used ; but I cannot make a satisfactory and simple com bination of as many as six or even of four pictures. 1 have described most of the plans that have occurred to me, but they all fail in some respect. The last I tried was a mosaic of pieces cut in the form of equilateral triangles, vertex outwards, from the rim of a large lens, and turned and brought close together with their vertices inwards. I then viewed the properly adjusted pictures through a small fixed telescope, in front of whose object-glass the mosaic was fixed. The method fails because the outer edges of the pictures are less bright than the inner ones i consequently the images are not equally mixed up. In conclusion, I can only express a wish that photo grapherswill try to make ethnological or family composites. 1 have been much pleased to find that both Dr. Billings, Surgeon-General of the War Department of the United States, and Mr. Thompson, lately attached to the Medical Department of the University of Edinburgh, and now to t i I § i t i 1 t